fs/Path: rename to AllocatedPath

The new class Path only holds a string pointer without being
responsible for allocation/deallocation.  The FileSystem.hxx library
accepts Path arguments instead of AllocatedPath, to avoid forcing
callers to allocate another string object.

src/fs/Path.hxx

@@ -24,50 +24,33 @@
 #include "Compiler.h"
 #include "Traits.hxx"
 
-#ifdef WIN32
-#include <glib.h>
-#endif
-
-#include <utility>
 #include <string>
 
 #include <assert.h>
+#include <string.h>
 
 class Error;
 
 /**
  * A path name in the native file system character set.
+ *
+ * This class manages a pointer to an existing path string.  While an
+ * instance lives, the string must not be invalidated.
  */
 class Path {
-	typedef std::string string;
-
 	typedef PathTraits::value_type value_type;
 	typedef PathTraits::pointer pointer;
 	typedef PathTraits::const_pointer const_pointer;
 
-	string value;
+	const char *value;
 
-	struct Donate {};
-
-	/**
-	 * Donate the allocated pointer to a new #Path object.
-	 */
-	Path(Donate, pointer _value);
-
-	Path(const_pointer _value):value(_value) {}
+	constexpr Path(const_pointer _value):value(_value) {}
 
 public:
 	/**
 	 * Copy a #Path object.
 	 */
-	Path(const Path &) = default;
-
-	/**
-	 * Move a #Path object.
-	 */
-	Path(Path &&other):value(std::move(other.value)) {}
-
-	~Path();
+	constexpr Path(const Path &) = default;
 
 	/**
 	 * Return a "nulled" instance.  Its IsNull() method will
@@ -75,70 +58,29 @@ public:
 	 *
 	 * @see IsNull()
 	 */
-	gcc_const
-	static Path Null() {
-		return Path("");
+	static constexpr Path Null() {
+		return Path(nullptr);
 	}
 
 	/**
-	 * Join two path components with the path separator.
+	 * Create a new instance pointing to the specified path
+	 * string.
 	 */
-	gcc_pure gcc_nonnull_all
-	static Path Build(const_pointer a, const_pointer b);
-
-	gcc_pure gcc_nonnull_all
-	static Path Build(const_pointer a, const Path &b) {
-		return Build(a, b.c_str());
-	}
-
-	gcc_pure gcc_nonnull_all
-	static Path Build(const Path &a, const_pointer b) {
-		return Build(a.c_str(), b);
-	}
-
-	gcc_pure
-	static Path Build(const Path &a, const Path &b) {
-		return Build(a.c_str(), b.c_str());
-	}
-
-	/**
-	 * Convert a C string that is already in the filesystem
-	 * character set to a #Path instance.
-	 */
-	gcc_pure
-	static Path FromFS(const_pointer fs) {
+	static constexpr Path FromFS(const_pointer fs) {
 		return Path(fs);
 	}
 
-	/**
-	 * Convert a UTF-8 C string to a #Path instance.
-	 * Returns return a "nulled" instance on error.
-	 */
-	gcc_pure gcc_nonnull_all
-	static Path FromUTF8(const char *path_utf8);
-
-	gcc_pure gcc_nonnull_all
-	static Path FromUTF8(const char *path_utf8, Error &error);
-
 	/**
 	 * Copy a #Path object.
 	 */
 	Path &operator=(const Path &) = default;
 
-	/**
-	 * Move a #Path object.
-	 */
-	Path &operator=(Path &&other) {
-		value = std::move(other.value);
-		return *this;
-	}
-
 	/**
 	 * Check if this is a "nulled" instance.  A "nulled" instance
 	 * must not be used.
 	 */
 	bool IsNull() const {
-		return value.empty();
+		return value == nullptr;
 	}
 
 	/**
@@ -147,7 +89,7 @@ public:
 	 * @see IsNull()
 	 */
 	void SetNull() {
-		value.clear();
+		value = nullptr;
 	}
 
 	/**
@@ -156,7 +98,9 @@ public:
 	 */
 	gcc_pure
 	size_t length() const {
-		return value.length();
+		assert(value != nullptr);
+
+		return strlen(value);
 	}
 
 	/**
@@ -166,7 +110,7 @@ public:
 	 */
 	gcc_pure
 	const_pointer c_str() const {
-		return value.c_str();
+		return value;
 	}
 
 	/**
@@ -175,7 +119,7 @@ public:
 	 */
 	gcc_pure
 	const_pointer data() const {
-		return value.data();
+		return value;
 	}
 
 	/**
@@ -186,13 +130,6 @@ public:
 	gcc_pure
 	std::string ToUTF8() const;
 
-	/**
-	 * Gets directory name of this path.
-	 * Returns a "nulled" instance on error.
-	 */
-	gcc_pure
-	Path GetDirectoryName() const;
-
 	/**
 	 * Determine the relative part of the given path to this
 	 * object, not including the directory separator.  Returns an
@@ -202,11 +139,6 @@ public:
 	gcc_pure
 	const char *RelativeFS(const char *other_fs) const;
 
-	/**
-	 * Chop trailing directory separators.
-	 */
-	void ChopSeparators();
-
 	gcc_pure
 	bool IsAbsolute() {
 		return PathTraits::IsAbsoluteFS(c_str());